1. Field of the Invention
The present invention relates to an analog/digital television signal receiver, and more specifically, to a digital/analog television receiver capable of receiving television signals in an ATSC and an NTSC system by a single tuner.
2. Description of the Prior Art
One example of such a kind of digital/analog television signal receiver is disclosed in, for example, Japanese Patent Laying-open No. 5-347736 [H04N 5/46, H04N 5/44, H04N 9/00] laid-open on Dec. 27, 1993 and Japanese Patent Laying-open No. 2000-59707 [H04N 5/44, H04B 1/16, H04B 1/26] laid-open on Feb. 25, 2000.
In such the digital/analog television signal receiver, due to a fact that a local oscillation frequency varied depending on an ambient temperature and a change over time in a case of receiving an analog television signal in the NTSC system, for example, an intermediate frequency signal was extracted after adjusting to an appropriate frequency by applying an automatic frequency control (AFC) (or an automatic frequency tuning (AFT)).
On the other hand, in a case of receiving a digital television signal in the ATSC-system, that is, an American standard, it did not require more than adjusting channel data of a frequency defined by the standard.
In this prior art, in a case of receiving the digital television signal, although the channel data defined by the standard was set, it was not possible to confirm whether or not a reception was made at a correct frequency. However, a digital television signal such as of the ATSC system is capable of reproducing (demodulating) and normally outputting images, sounds and etc. even if the frequency was deviated slightly. However, if a frequency deviation amount exceeds a permissive range, it was not possible to demodulate a television signal, and therefore, this led to a problem that a user could not enjoy a program on a channel selected by the user